Log warning messages from analysis steps not written to general stderr file

[morcuended]

Stderr/std log of batch jobs, which pipe all the LST-1 analysis steps, does not capture the warning messages from the lstchain scripts themselves. However, capturing all log messages from all the modules (above a given level of severity) is expected.

This was seen for example with subrun 02978.0091 from 20201120. This is the last subrun of the run and contains events with event_id=0 which gives a warning message if the r0 to dl1 lstchain script is run interactively. These warnings should be propagated to the stderr/out of the batch jobs.

Check how the stderr/out is captured in the subprocesses that run the lstchain scripts inside datasequence.py